SURVEY OF THE BRITISH ISLES FOR THE EPOCH JANUARY 1, 1886. 
65 
Kino'doin, and if the G.M.T. at which the observations were made is known they 
may be determined from the curves obtained at Kew. On the other hand the 
magnitude of the diurnal variation at a given instant depends on the local time, and 
in the case of stations so far apart as Kew and Valentia, the diurnal variation of the 
declination would, between 10 and 11 a.m. G.M.T., differ by several minutes of arc. 
We have therefore taken out from the Kew curves the deviations from the mean at 
the G.M.T. of our observations, and subtracting the corresponding value of the 
diurnal variations at Kew, have called these differences the temporary disturbances at 
the time of the observations. 
We have assumed further, that the Kew mean curves of diurnal variations may be 
taken as applying to the whole of the United Kingdom, but we have, in all cases, used 
the correction corresponding to the local time. Thus the total correction is the 
algebraic sum of the diurnal variation at the local time, and of the disturbance 
reeistered at Kew at the G.M.T. at which the observations were taken. 
O 
As proof of the validity of this method, we have picked out all the stations 
in Ireland at which two or more observations were made at times w'hen the diurnal 
variations differed by more than four minutes. 
As full particulars are given later on, it is only necessary here to tabulate the 
corrections for diurnal variation and disturbance in addition to the final results. 
It may, however, be remarked that in the majority of cases the determinations of the 
geographical, as well as of the magnetic meridian, are quite independent, and that at 
Athlone, Gort, and Westport, the results given were obtained on different days. The 
letters v and A are used throughout this memoir to indicate the departure from the 
mean value of the element at the time of experiment, due to diurnal variation and 
to temporary disturbance respectively. 
Station. 
V. 
A. 
Corrected 
Declination. 
Athlone . 
+ 6-3 
+ 1-5 
O 
22 
16-5 
- 3-9 
0-0 
22 
16-8 
Cavan . 
- 3-7 
+ 1-5 
22 
26-1 
+ 6-2 
- 4-0 
22 
26-7 
+ 3-5 
- 5-0 
22 
27-4 
Chaileville .... 
+ 4-9 
A I-O 
22 
19-4 
+ 0-7 
A 2-5 
22 
19-1 
Cork. 
0-U 
0-0 
22 
3-8 
+ 5-8 
- I-O 
2i 
1-7 
Gort. 
A 3-9 
- 1-0 
22 
.38-2 
- 4-2 
A 1-0 
22 
39-1 
Lismore . 
- 1-0 
0-0 
2L 
54-1 
+ 6-4 
4 3-5 
21 
54-0 
Westpoi’t . 
+ 0-7 
0-0 
23 
5-5 
+ 1-8 
- 0-5 
23 
4-2 
+ 6-3 
A 2 0 
23 
5-4 
MDCCCXC.—A. K 
